Improved skin substitute adherence, stretchability, and compliance for skin substitutes

ABSTRACT

An improved dressing is presented which enables quicker wound closure and a lower anesthesia requirement, comprised of an improved prior-art skin-substitute. The improvements consist of variations in the thickness of the woven portion of the dressing, to increase wound adherence.

RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 16/410,379, filed May 13, 2019 and a Continuation-In-Part ofU.S. patent application Ser. No. 15/396,720, filed Jan. 2, 2017, andthose applications are included here by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to primary dressings and bandages for both acuteand chronic wounds, particularly for burns.

BACKGROUND OF THE INVENTION

Over the past four and one-half decades of clinical use of bilaminatetemporary skin substitutes, Biobrane was found to be an idealreplacement for human skin (FHCA—frozen human cadaver allograft whichstill is the “Gold Standard”). The secondary adherence at 72 hours ofBiobrane (18/3 denier knitted nylon filament) was 200 grams per sq. cm.To vertically remove from the wound which is more than FHCA by about 50grams per sq. cm. of force, e.g. Woodroof E. A. Biobrane; A BiosyntheticSkin Prosthesis. In Wise D. Ed. Burn Wound Coverage.

It is desirable to have secondary adherence near identical to FHCA onexcised full-thickness wounds. In the last decade AWBAT® (advanced woundbioengineered alternative tissue)—15/2 denier and PermeaDerm® (15/1denier) have attempted to achieve the objective of enough but not toomuch secondary adherence. We have found a way to increase the thicknessof PermeaDerm® using 15/1 denier virgin nylon filament. A thicker 3D(three-dimensional) 15/1 denier PermeaDerm® knitted structure enablesgreater adherence as well as increased stretchability and compliance. Inthe early 1980's I used 15/1 denier nylon to make a less adherentBiobrane for protection of widely meshed autografts, clinicians calledit “light” Biobrane. Regular Biobrane was composed of 15/3 denier nylon.Also in the early 1980's International Paper Company created a siliconemembrane bonded to a plush nylon velour material as opposed to a knittednylon structure called IP-758 which had no biological coating nordrainage holes. Lack of drainage was related to increased infectioncomplication. IP-758 was too adherent and faded from the market quickly.

SUMMARY OF THE INVENTION

The present invention is a new approach to providing a glove and bootiebandage that addresses burn injuries. The state-of-art glove bandages donot possess the new features of the present invention, directed toallowing a measured amount of porosity, including essentially zeroporosity, and a lower cost to produce combined with shorterhealing/rehabilitation times of the burned hand.

The goal was to create a more effective biosynthetic glove for handburns management. An almost perfect anatomical fit for the hand reducingoperating room time and general anesthesia. A hydrophilic/hygroscopicmoist, but not wet, wound healing environment which enhances healing.

The present invention enables faster and better wound closure to fittingthumb and 3 fingers initially; then the clinician completes closure withstaples using greater circumferential elongation of the PermeaDerm® B(burn) material plus extra material on distil portion of hand. ThePermeaDerm® B material is a more sophisticated biological coating thancompeting materials such as Biobrane or AWBAT/AWBAT® Plus.

Wound sites have variable amounts of exudate/transudate/plasma present,from dry to weepy. The clinician must cleanly debride the wound, closeit and manage wound healing in a moist but not wet environment toachieve optimal results for both acute and chronic wounds. This isparticularly difficult with complicated structures like hands and feet.

The present invention provides a dressing that possesses all theproperties and attributes of an ideal skin substitute and, in addition,has ‘variable porosity’ controlled by the clinician from zero porosityto what the wound requires. The present invention enables the clinicianto move the fluid exuding from the wound through the primary dressinginto an absorbent secondary dressing without disturbing the kinetics ofhealing or causing pain to the patient.

The present invention will have a single layer of biologicals comprisedof a hypoallergenic BSE free USP Pharmaceutical grade gelatin, pure Aloeor Aloesin, pure Aloe and BSE free gelatin, or a mixture of pure Aloe,BSE free gelatin and ECM interact with the wound to stimulate the rateof healing while adherent to the wound. The bio-coat layer is depositeddirectly on the nylon side of the “variable porosity” silicone/nylonsurface and is stable for over three years at room temperature.

In vitro, the Aloe component has been demonstrated to cause a variety ofcells to attach and proliferate; as well as increase synthesis ofcollagen and alpha smooth muscle actin. ECM may be added to thebiologicals described above and is a mixture from human fibroblasts thatis known to cause rapid cell proliferation and tissue growth. Previouswound dressings and skin substitutes, as taught in U.S. Pat. No.7,815,931 contain gelatin, a pure Aloe component, chondroitin 4 & 6sulfate, and vitamin C & E. In contrast the current dressing will havetwo layers of biologicals applied in separate spraying operations asdescribed above. The first coat will contact the wound after the secondcoat of hypoallergenic bovine spongiform encephalopathy (BSE)-freeUnited States Pharmaceutical (USP)-grade gelatin interacts with fibrinin the wound to achieve early adherence, The second coat of biologicalsstimulates the healing process during the interval where the dressinginvention is in contact with the wound and is stable requiring 100degree water for 30 minutes to remove from the “variable porosity”silicone/nylon surface.

Human wounds vary in the following ways depending on location:relatively flat, convex or concave surface; and vary in movement fromminimal to a lot (diaphragm). Most difficult location to achieveadherence are convex wounds where there is movement (axilla, upperabdomen, etc.). Irregular depth wounds such as ulcers (DFU, VLU—diabeticfoot ulcer and venous leg ulcer) require prompt closure requiringexcellent compliance, stretchability or elongation.

If slow-healing ulcers (DFU, VLU, PU—pressure ulcer) are not closedpromptly infection complications may often occur and potential loss oflimb and compromise of life style is at risk. Clinical preference iscurrent PDB (average thickness is 0.0043″ with STDEV of 0.0003″) forprotection of widely meshed autograft where maximization of healing(definitive closure) of the interstices is desired. Too much adherence(greater than 50 gm per sq. cm. at 5 hours or 0.0048″ thick) will slowinterstices healing.

The PermeaDerm IFU (Instructions For Use) describe immobilization ofPermeaDerm for initial 24 hours to maximize early adherence. This iscommonly done except for the neck and abdomen adjacent to diaphragm.Bolstering techniques are frequently used to hold the bio-coated surfacein intimate contact with the debrided or excised hemostatic wound untiladherence.

A thicker 3D structure (average thickness 0.0080″ with STDEV 0.0008″)for PDG (PermeaDerm® glove) provides additional advantages over normalthickness PDG with respect to greater circumferential elongation and fitin the web spaces giving the clinician greater room for error during thefitting process. Once properly fitted, PDG will enable rapidrehabilitation without pain to regain full range of motion and willminimize interference with the healing process yielding excellentaesthetic and functional results. PDB and PDC (PermeaDerm® Chronic)would clinically benefit from both greater adherence and greaterelongation/conformability.

There is a regulatory advantage (FDA approval) based on use of samematerial (15/1 denier virgin nylon filament) to increase thickness of 3Dstructure of PermeaDerm® product as opposed to use of a different denierof virgin nylon filament (example 15/2, 15/3, 18/3 denier). Estimatedthickness using SEM: 15/1 denier about 0.0069″ and 18/3 denier about0.014″. 3D structure of 18/3 denier is about 103% (more than double)thicker than 15/1 denier.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1—The Biobrane® Glove—fabricated using two sheets of planarBiobrane 1982.

FIG. 2—AWBAT® Glove, a precision anatomical fit Biosynthetic Glove withthree-piece design in 2009. PermeaDerm® Glove is more practical andeffective.

FIG. 3—AWBAT® Bootie, a precision anatomical fit with three-piece design2009. PermeaDerm® Bootie is more practical and effective.

DETAILED DESCRIPTION

The present invention is a glove made by gluing two pieces ofPermeaDerm® together with the biologically coated 3D Gen 3 nylonstructure facing each other and the slitted silicone surface facing out,the 3D coated nylon surface contacts the wound surface inside the glove.For lower cost and efficiency, glue is preferred to seams sewn withthread.

The present invention is similar in composition to earlier skinsubstitutes in that they each have a thin silicone component and anunderlying 3D thin knitted nylon component. The present inventiondiffers from its ancestors in that it has “variable porosity” controlledby the clinician; the slit width in the thin silicone will beessentially zero (with no stretch, in relaxed mode) to a higher porosity(proportional to the stretch applied).

In addition, the present invention differs from prior art in thecomposition of biological coatings applied to both components and howthese coatings interact with the wound over time.

The preferred embodiment of the invention designed for burns, a regularpattern with slits on the silicone surface parallel to each other in thesame row is presented. The slits made in the silicone are approximately.0.125″ long with a space of 0.50″, between the slits; off-set parallelrows of slits are 0.25″ apart.

In this configuration the silicone/nylon membrane can be stretched in adirection perpendicular to the slit orientation and the slits will open.Porosity therefore increases proportionally to the amount of stretchapplied. Obviously, there is a maximum amount of stretching of thepreferred embodiment before the dressing fails. IFU (instructions foruse) describe a maximum of 20% elongation, well below the breakingpoint.

The use of the present invention has a large benefit because it isstable on the wound and possesses biologicals that aid in the healingprocess.

The present invention will have a single layer of biologicals comprisedof a hypoallergenic BSE free USP Pharmaceutical grade gelatin, pure Aloeor Aloesin, pure Aloe and BSE free gelatin, or a mixture of pure Aloe,BSE free gelatin and ECM interact with the wound to stimulate the rateof healing while adherent to the wound. The layer is deposited directlyon the nylon side of the “variable porosity” silicone/nylon surface andis stable for at least three years at room temperature.

The biologicals are applied to the knitted nylon side of the presentembodiment. Optionally, the biologicals can be applied to the siliconelayer as well.

Hand burns represent a small wound area with major potential fordisability. The management of hand burns is multidisciplinary, requiringthe expertise of surgeons, nurses, and occupational therapists. Inaddition to surgical excision and autografting, several wound healingmodalities are available for the care of hand burns including abilaminate, biosynthetic glove.

Motivated and reliable patients with burns limited to the hands can beappropriately managed on an outpatient basis at a burn center, where therequisite expertise in wound care, excision and grafting, andoccupational therapy are available. An increase in elongation andcompliance (greater 3D structure) of PermeaDerm results in improvementsof the following:

3D thickness of cured silicone nylon membrane: Preliminary thicknessdata of cured silicone/nylon membrane from the manufacturer, Jan. 9,2019 using micrometer: Gen1—Mean 0.0043″, STDEV 0.0003″, Min 0.0040″,Max 0.0048″. Gen3—Mean 0.0080″, STDEV 0.0008″, Min 0.0070″, Max 0.0095″.3D structure of Gen3 is about 86% thicker than Gen1. Conclusions onclinically effective adherence relative to thickness of a bilaminatesilicone/nylon membrane:

-   -   Less than 0.0040″—Inadequate adherence    -   Current PDB and PDC—Adequate adherence—average thickness 0.0043″        with STDEV 0.0003″    -   PDB, PDC and PDG with Gen3 nylon—Optimal Adherence—average        thickness 0.0080″ with STDEV of 0.0008″    -   Excessive adherence—thickness greater than 0.0095″        The preferred embodiment is the Gen3 PermeaDerm with average        thickness of 0.0080″ and STDEV of 0.0008″ which results in        Optimal adherence.

Before Slitting Gen1 Gen3 Gen3/Gen1 Average 0.0043″ 0.0080″ 1.86 STDEV0.0003″ 0.0008″ 2.67 Max 0.0046″ 0.0095″ Min 0.0040″ 0.0070″The glove and/or bootie made with an average of 0.008 inch thicknessnylon mesh is the preferred embodiment of the invention. The technologyto create the invention is listed in the preferred embodiment of thisinvention, but other methods are possible and are within thecontemplation of this patent.

What is claimed is:
 1. A bilaminate cured silicone/nylon material, thesilicone/nylon material comprised of two layers of material, the firstlayer of material comprised of a silicone membrane, the second layercomprised of a woven fabric, the two layers combined together with acombination means such that the two layers form a single structure, thepreferred combination method is heating, the first layer possessing aplurality of slits in its surface, said slits made after the two layersare combined, said slits in a regular pattern, the regular patterncomprising a parallel vertical orientation, said first layer and saidsecond layer treated with a coating comprised of one or more medicinalor therapeutic substances, the porosity of said skin substituteminimized to essentially zero porosity in the mode where no stretchingtension is exerted on the skin substitute, the porosity of said skinsubstitute variable proportional to the amount of stretching tension andthe direction in which said stretching tension is placed on the skinsubstitute, said second layer of material with a preferred range ofthickness of 15/1 denier knitted nylon of an average of 0.0080″ withSTDEV of 0.0008″.
 2. A bilaminate cured silicone/nylon material as inclaim 1 where there is an additional component of salinomycin, nativehigh molecular weight collagen, and Mafenide Acetate in the biologicalcoating.
 3. A bilaminate cured silicone/nylon material as in claim 1using a denier virgin nylon filament of 15/2 or 15/3 with range ofthickness 0.0040″ to 0.0095″.
 4. A bilaminate cured silicone/nylonmaterial as in claim 1 where said coating is a single layer ofbiological substances comprised of a. a hypoallergenic BSE free USPPharmaceutical grade gelatin, b. pure Aloe or Aloesin, c. pure Aloe andBSE free gelatin, or a mixture of pure Aloe, BSE free gelatin and ECMand where said coating interacts with a wound to stimulate the rate ofhealing while adherent to the wound, the coating deposited directly onthe woven fabric, said coating chemically stable for at least threeyears at room temperature.